Hot gas generators have long been utilized for producing hot gas under pressure to operate engines of various sorts as well as for other purposes. See, for example, U.S. Letters Pat. No. 1,828,784 issued Oct. 27, 1931 to Perrin which constitutes the most pertinent prior art known to the applicant.
In such hot gas generators, a carbonaceous fuel is combusted with an oxidant to produce hot gases of combustion. In addition, additional fuel may be introduced into the hot gases of combustion to be vaporized, as opposed to combusted, to increase the volume of hot gas while bringing the temperature of the combustion gas down to some desired temperature incapable of causing damage to the system in which the generator is used.
One difficulty in the operation and use of such hot gas generators is carbon build-up. Carbon build-up results when the fuel is not completely oxidized and elemental carbon is formed within the combustion chamber of the generator. It may deposit itself at various locations therein, particularly those running at relatively cool temperatures. While carbon build-up can be avoided by providing the generator with an excess of oxidant, this may result in the generation of hot spots within the vessel defining the combustion chamber causing damage thereto. Consequently, it is conventional practice to run a hot gas generator on the rich side so that all oxidant available for combustion is consumed to prevent the existence of hot spots; and this raises the potential for carbon build-up.
As pointed out by Perrin in his previously identified United States Letters Patent, it is also desirable to cool the combustion chamber to prevent damage thereto by excessive heat from combustion occurring therein. Advantageously, this is accomplished by cooling the combustion chamber with fuel. However, in the Perrin construction, there is the opportunity for excessive cooling of the combustion chamber walls; and the resulting cool spots facilitate carbon build-up when the generator is operated on the rich side as is desired to prevent the existence of hot spots.
Carbon build-up is undesirable because it may interfere with heat transfer. However, another problem resulting from carbon build-up is much more serious Specifically, such hot gas generators are frequently used to produce hot gases for driving turbine wheels. As carbon builds up, particles of the same typically break free and then flow with the hot gas through the turbine wheel. Such particulate carbon not only erodes the turbine nozzles and the turbine wheels, but it additionally can cause surge.
The present invention is directed to overcoming one or more of the above problems.